A known electric pump is disclosed, for example, in JP2003129966A. In the electric pump, a motor portion (MT), having a configuration of a brushless motor, is used for driving the pump portion (PM) so as to prevent short-circuits due to a usage of fluid (e.g. hydraulic oil).
Further, in the electric pump, an inscribed-type pump is used as the pump portion, and such the inscribed-type pump is positioned inside the motor portion so as to downsize the electric pump in an axial direction. Specifically, a core of the motor portion is embedded in a housing, and a permanent magnet, which faces the core in contiguity therewith, is supported so as to rotate relative to the same axis as that of the core. An outer rotor of the pump portion is fixed at the permanent magnet so as to rotate integrally therewith. An inner rotor, having a central axis eccentric from a central axis of the core or the like, is supported within the outer rotor. In this circumstance, within the motor portion, the inner rotor rotates in accordance with the rotation of the outer rotor (and the permanent magnet) so as to carry out intake and exhaust of fluid.
According to the know electric pump, the permanent magnet fixed to the outer rotor slides on an inner peripheral surface of the housing at which the core is embedded. In this circumstance, the inner peripheral surface of the housing, which is molded by use of resin, or the outer peripheral surface of the permanent magnet wears so as to decrease the duration of life thereof.
Thus, a need exist for an electric pump having an inscribed-type pump to expand the duration of life thereof.